Since the mid-1940s, perchlorate, and in particular ammonium perchlorate, has been used in the production of solid rocket fuel for military and space applications. Additionally various perchlorate salts have been used in a wide variety of non-military applications. For example, perchlorate salts are used in the production of matches, safety flares, fireworks and other pyrotechnics.
That past use of perchlorate has given rise to a significant present problem of perchlorate contamination of soil and ground water. The perchlorate contamination is a significant problem because it is potentially toxic. In particular, ingested perchlorate interferes with the thyroid gland's ability to utilize iodine, an essential nutrient. As a result, production of thyroid hormones that regulate metabolism and growth may be disrupted. Although short-term fluctuations in thyroid hormone levels are normal and the body has a certain capacity to cope and adjust for these small changes, continuous thyroid disruption may cause an imbalance, especially when a body is already under stress.
Since the perchlorate contamination threat was identified, various efforts have been initiated with the purpose of establishing goals and regulatory standards. In 2004 , the California Office of Environmental Health Hazard Assessment published a public health goal of 6 ppb. In addition, the U.S. Environmental Protection Agency has proposed a limit for perchlorate of 24.5 ppb and the Massachusetts Department of Environmental Protection has proposed a limit of 2 ppb.
In view of the existing and impending restrictions on perchlorate in potable water, various attempts have been made to provide apparatus and methods for removing perchlorate from water. Various attempts have been made to remove perchlorate from water using microorganisms. For example, the bacterium, Perc 1 ace, has been used in a flow-through system to reduce perchlorate in water. In that system, contaminated ground water flowed through a bacterially active zone of a bioreactor and was exposed to Perc 1 ace. Although the bacterium was effective in reducing perchlorate, the presence of microorganisms creates various disadvantages. One disadvantage is that the costs are increased due to precautions that must be taken when handling the microorganism, including additional and potentially costly disinfection procedures. Furthermore, systems without microorganisms are easier to handle and more responsive to varying operational conditions.
Another example of a system for removing perchlorate is provided in U.S. Pat. No. 6,531,065 to Gurol et al. In that patent it was shown that zero-valent iron particles can reduce perchlorate to chloride ion, and furthermore that ultra-violet (“UV”) radiation can serve as a catalyst for the reduction process. The process involved adding large scale particles of zero-valent iron (in the millimeter range) to perchlorate-containing water in special reactors that accommodate UV radiation tubes.